Vulcanization of rubber



Patented Sept. 27, 1938 2,131,126

. 2,131,126 1 VULC'ANIZATION F RUBBER William P. ter Horst, Packnack Lake, N. I, as

signor to United States Rubber Company, New York, N. Y., a corporation of New Jersey No Drawing. Application April 1, 1931, Serial No. 527,056

6 Claims. (01. 18-53) This invention relates to mixed oxalates ofture exceeding 80 degrees C. 21 grams diphenylaryl-substituted guanidines, and is herein illusguanidine and the temperature is gradually trated as embodied in carbo-xylic esters such as v raised to boiling. The diphenylgu'anidine goes the oxalates of basic rubber accelerator mateinto solution in the form of the acid oxalate. The

rials or compositions containing the same. The solution is then filtered from a small amount of f oxalates which are the mixed oxalates of organic water-insoluble material and the filtrate is alamino compounds are useful as plasticizers, espelowed to cool. Diphenylguanidine acid oxalate cially for rubber which requires calendering after separates out and is filtered, washed and dried; vulcanization. The product so obtained is a whitepowder melt- 10 It has been known that many amines were acing at'approximately 168 degrees C. with decomcelerators, adapted to produce rapid vulcanizaposition. tion, but the rubber containing them and mer- For test purposes the followingrubber mix was captothiazole vulcanized so rapidly and at such used: smoked sheets 100 parts, sulfur 3 parts,

a low temperature that the rubber scorched or zinc oxide 5 parts, stearic acid 1 part. Two mixes incipiently vulcanized in the mill. were made. One mix contained one part of 2- 15 The material of the present invention is well mercaptobenzothiazole as the accelerator and the adapted to be used with the compound 2-merother mix contained .3 part Z-mercaptobencaptobenzothiazole. When so used, it has a diszothiazole and .7 part diphenylguanidine acid tinct plasticizing action, like other mono-amino oxalate. Ascorch test showed that the stock concompounds; moreover it speeds vulcanization taining one part 2 mercaptobenzothiazolev 20 when so used but does not cause the premature scorched after running in the mill five hours at vulcanization in the mill caused by practically 80 degrees C. whereas it took eleven hours at 80 all free amines when used with Z-mercaptobendegrees C. before scorching took place with the zothiazole. stock containing a combination of Z-mercapto- It will be observed in the data given below the benzothiazole and diphenylguanidine acid oxa- 25 decomposing point of the new oxalates used is late. The following test results were obtained: well above the usual temperature of vulcaniza- UNITED STATES PATENT o os tion, yet in the mold the activating oxalate cou stock containingj operates with the 2-mercaptothiazole as if they SW01 containing Pm F In other words the new material has tamed Cure 55 1 5 plliinylguanlidine the Z-mercaptobenzothiazole on the mill and has f ti g $5 13,; activated it in the mold. The rubber after vulinch inlbs-pefsquare canization has the so-called snappy quality of the I um rubber ordinarily obtainable at low temperature 0 35 vulcanization and yet the small quantity needed 11 3 1; of the new oxalates reduces accelerator costs. It 15 mill. at 270 FIIIIIIII V 2:650 21725 enables softeners to be reduced or dispensed with, 30 2 F 4,725 and eifects a better dispersion of carbon black.

40 It is found that oxalates may speed vulcaniza- Example diphenylguanidine 0X9:- 40

tion to be even faster than with 2-mercaptobenlate may be prepared by adding One mole izothiazole, though avoiding scorching in the mill, Phenylguanidine a So ution of One mole dias mentioned above. They thus are not open to Phenylguanidine acid Oxalate in W t r- The the objection that they slow up vulcanization as neutral diphenylguanidine oxalate is a white do acetic acid compounds. pow r h v a melting point pp im tely' 45 The oxalate compounds which effectuate the 220-225 degrees With p t onplasticizing have all the advantages of aniline E-lfample miXedOXalate p y uaniwithout the objection of being poisonous, th bdine ammonium oxalate was obtained as a white jection which has prevented the use of aniline. Powder when excess ammonium hydroxide w Moreover they are often effective when as little added to a 1101? o o o diphenylguanidine 50 as a quarter of one per cent is used. acid oxalate. v

Example 1.Diphenylguanidine acid oxalate Example 4.-The mixed oxalate diphenylguanimay be prepared as follows. 12.8 grams oxalic dine urea oxalate was obtained when one mole acid (COOH)2, 2H2O are dissolved in 300 grams urea was added to a hot solution of one mole di v water. To this solution is added, at a temperaphenylguanidine acid oxalate. This product is a 55' White powder which melts at approximately 168 degrees C.

Example 5.--Diphenylguanidine-aniline oxalate. This product is obtained by adding one mole diphenylguanidine to a solution of aniline acid oxalate in water or by adding one mole aniline to a hot solution of diphenylguanidine' acid oxalate. This white powder product melts at approximately 220 degreesC. with decomposition.

tioned as activated by the suitable oxalate other disulfides. For example, 2-mercaptotolylthiazole, chloro-2-mercaptobenzothiazoles, nitro-Z-mercaptobenzothiazoles, and others. may also be used in admixture orcombination with esters of Z-mercaptobenzothiazole as, e. g;, with the 2-4-dinitro-phenyl-ester or the chloro-ace tone esters of mercaptobenthiazole.

Accelerators may also be made by producing the monophenylguanidine oxalates, phenylorthotolylguanidine oxalates, diorthotolylguanidine oxalates, phenylbiguanide oxalates, and orthotolylbiguanide oxalates.

The oxalates, as mentioned above, exert a favorable plasticizing action on the rubber. They yield a rubber which is softer before as well as after vulcanization. Besides the oxalates mentioned the following amines have been found to yield oxalates, neutral as well as acid which have great plasticizing power: urea, aniline, orthotoluidine, mixed toluidines, phenetidines. In this Instead of the2-mercaptobenzothiazole men;

mercaptothiazoles may be used as well as their The oxalates respect the oxalates, of diphenylethylenediamine and diphenylpropylenediamine have also been found to have remarkable plasticizing properties.

Having thus described certain embodiments of the invention, what is claimed is:

1. The substance diphenylguanidine ammonium oxalate. I

2. The process of making vulcanized rubber which consists in mixing a vulcanizable rubber composition with a mercaptothiazole accelerator and a mixed oxalate of an aryl substituted guanidine andthen heating it.

3. The process of making vulcanized rubber which consists in mixing a vulcanizable rubber composition with a benzothiazyl sulphide accelerator and. a' diarylguanidine ammonium oxalate.

4. The process of making vulcanized rubber "Whichjconsists in mixing a vulcanizable rubber composition with a mercaptothiazole and a mixed oxalateof diphenylguanidine, and then heating it. I I

5. The process of making vulcanized rubber whichconsists in mixing a vulcanizable rubber composition with a mercaptobenzothiazole and.

with amixed oxalate of an aryl substituted guanidine, and then heating it.

6. Theprocess of making vulcanized rubber which consists in mixing a vulcanizable rubber composition with a mercaptobenzothiazole and with a mixed oxalate of diphenylguanidine, and then heating it.

' WILLIAM F. 'IER HORST. 

